Soil compaction machine



Dec. 27, 1955 J. L. MCRAE 2,728,277

SOIL COMPACTION MACHINE Filed Dec. 18, 1952 IN V EN TOR.

Jain l nz'aay fife/Fae BY 2 6414 -1 United States Patent SOIL COMPACTION MACHINE John L. McRae, Vicksburg, Miss.

Application December 18, 1952, Serial No. 326,802

' 4 Claims. (or. 94-48) (Granted under Title 35, U. S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without payment to me of any royalty thereon.

The present invention relates to an improved machine for compacting soils to develop a solid earth surface as for a base for roads, airstrips or construction sites by a tamping operation.

Prior machines for accomplishing this purpose have been of several types. One type used compacted the earth solely by the pressure of a large mass of weight in the form of a roller, a plurality of rollers or slides. Because these machines depended solely upon the squeezing action resulting from surface pressure to compact soils, they did not always overcome the friction among particles of the soils with the result that the soils were not sutficiently compacted to develop a shear strength comparable to soils tamped by the impact of a tamping device of small area of impact, such as a heavy rod.

Another classification of machines used was essentially a heavy roller but included a vibrator which added a vibratory impulse to the squeezing action of the heavy roller with the result that the friction among the soil particles was partially overcome by vibration of the column of soil beneath the rollers which caused the particles to move somewhat with respect to one another and develop a more compact mass than would result solely from squeezing action. However, even this type machine does not compact soil comparable to the effect obtained by tamping with a heavy device of small area of impact.

An important object of this invention is to provide a machine that will compact soil by a tamping action.

Another object of this invention is to provide a mobile machine that will compact soil by the tamping action of a plurality of tamping members of small area of impact.

Another object of this invention is to provide a mobile machine that will compact soil by a plurality of tamping members caused to strike the soil by an oscillator including eccentric weights oppositely revolving in a common plane.

Another object of this invention is to provide an oscillator for a soil compaction machine that will cause the entire machine to repeatedly strike the soil with a tamping action.

Another object of this invention is to provide a mobile machine that will compact soil by the action of a plurality of tamping members striking the soil with an impact force in excess of the weight of the entire machine.

Briefly, in accordance with this invention, there is provided a dynamic soil compacting machine in the form of a trailer adapted to be coupled to a tractor or other prime mover including a source of power. The compacting machine includes a plurality of disc shaped tamping members freely revolving about their centers on a common axis suspended from a frame which also supports an oscillator mechanism driven by a flexible connection with the said source of power. The oscillator mechanism includes eccentric weights arranged for angularly equivalent opposite revolution in a common plane about spaced axes wherein 2,728,277 Patented Dec. 27, 1955 the mass of the revolving weights and the radius of revolution are so proportioned to the mass of the entire machine that the entire machine will jump up and down as it is towed causing the disc shaped tamping members to repeatedly strike the soil with a tamping impact.

In the accompanying drawings, forming a part of this specification and wherein like numerals are employed to designate like parts throughout the same:

Fig. 1 is a side elevation, partly in vertical section, of the invention including a portion of a tractor vehicle furnishing a source of power and showing the oscillator mechanism in side elevation;

Fig. 2 is a plan view of the machine with the cover removed showing the oscillator mechanism in plan; and

Fig. 3 is an end elevation with a portion of the housing broken away showing the oscillator mechanism in end elevation.

In the drawings, wherein for the purpose of illustration there is shown a preferred embodiment of the invention, the dynamic soil compaction machine is indicated generally by numeral 1 and includes a frame 2, an impact structure 3, a housing 4, a flexible power transmitting mechanism 5, and an oscillator mechanism 6 within the housing 3.

The frame 2 of the machine is constructed of a horizontal platform 20 with side members 21 and intermediate members 22 depending therefrom normally in a line transversely of the platform, re-enforcing members 23 connecting the free ends of side members 21 to platform 20 at points spaced from the base ends of side members 21, and a tow-bar 24 which may be attached to a trailer hitch 7 of a tractor vehicle 8. The tractor hitch 7 includes a U member 9, resilient shock absorbing members 10 and a pin 11.

The frame 2 carries thereunder an impact structure 3 including an axle 3t) journaled in bearings 25 in side members 21 at the junction of re-enforcing members 23 and in bearings 26 in intermediate members 22, and a plurality of discs 31 and spacers 32 alternately journaled on axle 30 for free rotation thereabout.

The frame 2 also supports a rectangular housing 4 of sheet work including an interior wall extending transversely of the machine dividing the housing into a gear chamber 41 and an oscillator chamber 42.

The power transmitting mechanism 5, which is used to transmit power from the source of power on the tractor vehicle to the oscillator mechanism 6, includes a universal joint adapted for connection to a source of power 51 on the tractor vehicle, a universal joint 52 attached to primary shaft journaled in bearings 61 which are attached to walls of housing 4, and a coupling consisting of a hollow rectangular shaft 53 attached at one end to universal joint 50 and a solid rectangular shaft 54 attached to universal joint 52 at one end thereof and having the other end slidably received within the hollow shaft 53. This arrangement permits an even transmittal of power from a source of power, as 51 on the tractor vehicle, to the shaft 64) in the gear chamber 41 of the housing 4 regardless of the direction and distance between the source of power 51 and the shaft 60 because universal joints 5i) and 52 compensate for the directional variances between those two elements and the shafts 53 and 54 compensate for the changes of distance between those twoelements.

Primary shaft 60 journaled in bearings 61 attached to walls of the housing 4 extends through gear chamber 41 and has afiixed thereon, for rotation therewith, primary gear 62 which meshes with a secondary gear 63 within the gear chamber 41 mounted on secondary shaft 64 for rotation therewith. Secondary shaft 64 is journaled in bearings 65 attached to walls of the housing 4 and extends through both the gear chamber 41 and the oscillator chamber 42.

The oscillator mechanism: 6 includes that portion of the,secondary shaft. 64 extending through theoscillator.

shaft 64 on either side of gear 66; parallel rods 72' and,

73 threaded into collars and 71 respectively; weight 74 adjustablyattached to rods 72 being secured thereon by adjusting nuts 75; and weight 76' adjustably secured on rods 73, being secured thereon by adjusting nuts 77. This'arrangement, because of the parailelalignment of rods 72 and 73, permits weights 74 and 76 to be rotated about shaft 64'to develop a centrifugal force in concert, and because of the variable radius of rotation, dependent upon the position of the weights 74 and 76 upon rods 72' and 73 as determined by the adjusting nuts 75 and 77; permits adjustment of the amplitude of the resulting centrifugal force. The eccentrics also include collars 80 and 81 locked to shaft 68 on either side of gear 67; parallel rods 82 and 83 threaded into collars 80 and 81 respectively; weight 84 adjustably attached to rods 82, being secured thereon by adjusting nuts 85; and weight 86 adjustably secured on rods 83, being secured thereon by adjusting nuts 37. This arrangement is identical with that of collars 70 and 71 and weights 74 and 76 described above with the exception that because shafts 64 and 68, to which the two sets of collars and weights are attached, revolve in opposite directions as determined by meshed gears 66 and 67, the weights 84 and 86 revolve eccentrically in a direction opposite to weights 74 and 76. It is necessary in this structure, that the rods and weights by so located with respect to the axes of rotation that the rods carrying weights 84 and 86 extend in directions having the same vertical components but having opposite horizontal components from the axis of rotation as compared with the rods carrying weights 74 and 76 in every position of revolution; and as shown in Figs. 2 and 3, rods 72, 73, 82 and 83 extend in a common plane oppositely from their respective axes of rotation and rotate in opposite directions through to another.

position in a common plane where they extend toward one another in order that the centrifugal force of all the weights is cumulative in vertical directions and self-cancelling in horizontal. directions. If the rods and weights were placed other than as described above, the centrifugal force developed by one set of Weights in the vertical directions, as for example Weights 84 and 86, wouldnegafive a portion of the centrifugal force in the vertical directions developed by weights 74.and 76; or theentire unit wouldfldevelop a vibration or movement in horizontal directions.

In operation the dynamic soil compaction machine 1 isv attached to a tractor. vehicle and the power transmitting mechanism 5 is attached to a source of power carried by the tractor vehicle. Power transmitted by the power transmitting mechanism 5 to the, gear train, including gears 62 and 63, propels the oscillator mechanism 6 causing weights 84 and 86 to rotate centrifugally about shaft.

vertically with each revolution-of the weights Without oscillation parallel to axle 30. By adjustment of adjusting nuts 75, v77, 85 and 87, moving Weights74, 76', 84 and 86 longitudinally ofrods 72, 73,*82'and- 83;"the

4.; radius of rotation of the weights may be varied so as to permitthe selection of a' centrifugal force which, exerting itself vertically of the machine as illustrated in Fig. 3 would develop a vertical oscillating force in excess of the total weight of the machine causing the whole machine to jump up and down striking the soil to be compacted with discs 31 on the downward stroke. Likewise the centrifugal force might be varied by changing the speed of rotation of the weights or by changing the mass of the weight. The impact of discs 31 on the downward stroke will cause discs 31 to cut through an accumulation of loose soil to the firm base beneath where the discs 31 will ramp a portion of the loose soil onto the firm base. Repetition of this action will compact the loose soil progressively from'the-bottom of the layer of loose soil so that after several passes of the machine, an entire layer of loose soil may be compacted onto the solid base. It may be seen that a solid surface may be; built up by spreading a layer of loose soil which is somewhatless in thickness thanv the radius of discs 31 and may becompacted into a solid layer by passing the compaction machine overthe layer several times, and that progressive layers of loose soil may be compacted onto a firmbase. The net result of the operation of the machine, as described, is that loose soil may be compacted to a density and shear strength heretofore gained only by theuse of repeated tamping.

with an object of small area of impact as, for example, a heavy rod.

The force by which discs 31 may be made to impact the loose substance worked upon may conveniently be 1 illustrated by reference to data worked out for a minia;

ture model of the machine and which are:

Centrifugal force developed by a revolving eccentricweight=F=Mrw where:

M mass of eccentric W=weight of eccentric g 32.2 ft./sec =accelerati0n due to gravity r=.1.17 in.=distance from axis of rotation to mass center. of eccentric weight w=angular velocity of eccentric in radians/sec.

Using this formula the following data are calculated:

Total centrifugal force, lb.

Centrliugal force for one eccentric, lb.

, w R. P. M.. Radium/sea (R. P. M.=revolutions per minute for eccentrics.)

Having thus described my invention, what I claim as new and wish to secure by Letters Patent is:

l. A machine for compacting soil as it is towed thereover-by a prime moverhaving a source of power thereon comprising a trailer frame, an oscillating mechanism supported by the frame, a power transmitting mechanism connected to the oscillating mechanism and adapted to be connected to a source of power on a prime mover, said oscillating mechanism including eccentrically, ad: justably mountedweights and a plurality of parallel shafts forsupportingsaid Weights driven by said power transmitting mechanism, thecenters of gravity of said eccentrically mounted weights being located for rotation when in operating position, said elements being suspended beneath the frame and rigidly secured thereto for imparting sharp tamping impacts to the soil operated on.

2. The structure of claim 1 wherein the impact struc ture includes an axle separated from but rigidly secured to said frame and extending transversely of the machine, said axle being normal to the axes of said plurality of parallel shafts and a plurality of discs and spacers alteruately journaled on the axle for free rotation thereabout, whereby forces created by the oscillating mechanism are transferred to the surface acted upon by said discs without intervening dampening means.

3. A machine for compacting soil as it is towed thereover by a prime mover having a source of power thereon, the machine comprising a frame, an oscillating mechanism supported by the frame, power-transmitting mechanism connected to the oscillating mechanism and adapted to be connected to the source of power on the prime mover, and an impact structure suspended beneath the frame for imparting a tamping impact to the surface of soil being compacted; the impact structure including an axle extending transversely of the machine and a plurality of discs and spacers alternately journaled on the axle for free rotation thereabout; the oscillating mechanism including a first oscillator gear wheel, and a second oscillator gear wheel, the gear wheels havinga 1:1 ratio and being meshed together in a common plane, a first shaft supported by bearings and extending axially through the first oscillator gear wheel and being attached thereto for rotation therewith, a second shaft supported by bearings and extending axially through the second oscillator gear wheel and being attached thereto for rotation therewith, eccentric weights carried by each shaft on. each side of each oscillator gear wheel, rod means attaching the eccentric weights to each shaft, and means adjustably attaching each of the weights to the rod means to vary the effective radius of gyration of the weights; said weights on each shaft being located in the same direction from the axis of the shaft, said weights attached to the second shaft being in a direction from the axis of that shaft having the same component of direction normal to said axle as the weights on the first shaft and having the opposite component of direction parallel to said axle from the weights of the first shaft, whereby revolution of the shafts will cause the weights to produce a centrifugal force that is cumulative in the directions normal to said axle and self-cancelling in the directions parallel to said axle.

4. A machine as recited in claim 3 wherein the axis of each of said first and second shafts is normal to the axis of said axle carrying said plurality of discs, and the center of gravity of each of said eccentric weights is located in a plane normal to the axis of the corresponding one of said first and second shafts for rotation thereabout whereby revolution of said shaft produces a centrifugal force that is cumulative and imparts a variable vertical oscillatory motion to said axle which exceeds the force on said axle due to the weight of the machine.

References Cited in the file of this patent UNITED STATES PATENTS 1,831,116 Huntley Nov. 10, 1931 2,018,294 Baily Oct. 22, 1935 2,466,822 Pollitz Apr. 12, 1949 2,677,995 Wood May 11, 1954 

